When drilling using a drill bit, it is possible to use a drill bush to guide the drill bit. In this case, the axis of the drill bush is merged with the axis of the hole to be produced.
When it is necessary to produce a number of drill holes in one and the same area of a part, it is possible to use a drilling template in the form of a plate provided with a number of holes positioned relative to one another in accordance with the positions of the holes to be produced in the part. This drilling template is placed between the part to be drilled and the tool and is positioned relative to the part in such a way that the axes of the holes of the template are merged with the axes of the holes to be produced. The holes of the template make it possible not only to position the end of the tool relative to the front surface, but also to position the tool according to a determined angle of attack relative to the front surface.
Hereinafter in the description, “front surface” will be understood to mean the surface via which a tool penetrates to perform a machining operation.
Depending on the applications, the holes of the drilling template may be each equipped with a drill bush in order to reduce their wear.
According to one procedure, the operator positions the drilling template relative to the part. Then, he or she can produce the holes by positioning, for each of them, the tool relative to the corresponding template hole. Ideally, for each hole to be produced, the viewing axis of the operator should form a small angle with the axis of the hole of the template corresponding to the hole to be produced for positioning the tool.
In the aeronautical field, drilling templates can be used when manufacturing and assembling parts.
In certain circumstances, it is necessary to work in the aircraft to produce holes, for example for maintenance operations. To execute drill holes, the operator can use a hand-held tool, such as a portable drill. This drill comprises a body (possibly with a handle) and a head linked to the body supporting a cutting tool such as a drill bit for example. Advantageously, the head comprises suction for sucking the chips generated in the machining and discharging them via a discharge duct.
To produce a hole, the operator positions the end of the drill bit on the axis of the hole to be produced, then exerts a force to generate a movement to advance the drill bit which, when combined with the rotation of the drill bit, generates the machining.
As indicated previously, in order to correctly position the tool relative to the hole to be produced, the viewing axis of the operator should form a small angle with the axis of the hole to be produced. Moreover, during the drilling operation, the operator should be correctly positioned relative to the hole to be produced so as to exert a force in the direction of the axis of the hole to be produced in order for the hole to be correctly produced in accordance with the geometrical and dimensional tolerances.
Certain areas of the aircraft, such as, for example, the join between the fuselage and the wings, are areas that are difficult to access and confined. In certain cases, the operator cannot be correctly positioned to the drill holes to be produced so that his or her viewing axis is not optimally positioned to facilitate the positioning of the tool relative to the drill holes to be produced. Furthermore, when not correctly positioned, it is difficult for the operator to exert a force on the tool that is always correctly oriented relative to the axis of the drill hole to be produced.
The operator could consider positioning a drilling template with holes that are aligned with the drill holes to be produced. However, even in this case, it would be difficult for the operator not correctly positioned relative to the drill hole to be produced to position the tool relative to the holes of the drilling template and exert a force on the tool that is always correctly oriented relative to the axis of the drill hole to be produced.
Consequently, the drilling operations in confined areas of the aircraft are lengthy and difficult to carry out.
According to another issue, the operator may be required to perform, in these confined areas of the aircraft, more complex machining operations than holes. These complex machining operations are, like those for the drill holes, lengthy and difficult to perform.
To perform complex machining operations, there are copying techniques that use a pantograph. A device making it possible to implement such a technique is described in the document EP-1.978.889 and comprises a pantograph in the form of a deformable parallelogram with four sides hinged in pairs, along mutually parallel articulation axes. A first side of this pantograph is securely attached to a moving carriage which can be moved in a plane. The pantograph supports a pointer securely attached to a second side that is articulated relative to the first side and a tool securely attached to a third side parallel to the second side and articulated relative to the first side, the pointer and the tool being spaced apart from the first side. The tool has a rotation axis parallel to the articulation axes and parallel to the plane of movement of the carriage. This architecture does not make it possible to produce drill holes.
Consequently, there is no multipurpose machining device that makes it possible to perform drilling and machining operations by copying with a guidance system spaced apart from the tool.